Circuit controlling device



Jan; 20, 1942. c. w. KUHN Em. 2,270,736

CIRCUIT CONTROLLING DEVICE Filed NOV. 15, 1939 the aforementionedobjection.

Patented Jan. 20, 1942 UNITED STATES PATENT OFFlCE 2,270,736 cmcm'rcon'raomno nnvrca Clarence W. Kuhn and Robert 0. Perrine, Wauwatosa,Win, asslgnora to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation ofDelaware Application November 15, 1939, Serial No. 304,626

4 Claims. (CL-200-1 40) This invention relates to circuit controllingdevices, and more particularly to thermo-responsive switches forcontrolling electric refrigerators.

Electric refrigerators are commonly controlled by a thermo-responsiveswitch which is manually adjustable to select temperatures within agiven range known as the cold control range and to also provide anabnormally high temperature for defrosting. Such control switches areordinarily provided with a gas filled temperature responsive operatingbellows having a helical loading spring associated therewith whichcounteracts expansion of the bellows and is adjustable by means of ascrew to vary the temperature values at which the refrigerator isstarted and stopped. The adjusting screw is usually of uniform pitch andhas an adjusting knob or lever fixed thereto which cooperates with astationary dial to indicate the temperature setting of the switch.

It is desirable in switches of the aforesaid type that the requiredrange of cold control temperatures and also the relatively highdefrosting temperature be obtained within one revolution of theadjusting screw. However, it has heretofore' been found dimcult, and insome cases im- .possible, to obtain such temperatures within a singlerevolution of the adjusting screw without narrowing to an objectionabledegree the range of movement of the screw for effecting selection of thetemperatures within the cold control range.

The'present invention has among its objects to'provide an improvedadjusting mechanism for switches of the aforesaid type which overcomesAnother object is to provide an improved adjusting mechanism forswitches of the aforesaid .type which effects adjustment of the loadingspring at an increasing rate upon movement of the adjusting knob fromthe cold end to the warm end ofits cold control range.

Another object is to provide an improved adjusting mechanism which canbe readily applied to existing types of thermo-responsive switcheswithout material modification of the, switch structure.

Another object is to provide an adjusting mechanism of the aforesaidtype which is simple in construction and exceedingly positive andreliable-in operation.

Various other objects and advantages of the invention will hereinafterappear.

The accompanying drawing illustrates an embodiment of the inventionwhich will now be described, .it being understood that variousmodiflcations may be made in the embodiment illustrated withoutdeparting from the spirit and scope'of the appended claims.

In the drawing:

Figure. 1 is a side view of a thermorresponsive switch embodying theinvention, the switch being shown in closed position and the enclosingcasing therefor being shown in section;

Fig. 2 is a view similar to Fig. 1, illustrating the switch in circuitopening position, and also illustrating certain of the switch operatingparts in section;

Fig. 3 is a front elevational view of certain of the operating parts ofthe adjusting mechanism shown in Figs. l and 2, and

Figs. 4 and 5 are diagrammatic views illustrating various settings ofthe operating parts shown in Fig. 3.

Referring to Figs. '1 and 2, the invention is shown inconnection with athermc-responsive switch. of the type disclosed in the patent to C. W.Kuhn, No. 2,158,824, of May 16, 1939. However, the switch shown ismerely selected'to illustrate a practical application of the inventionand as is apparent the invention may be applied to switches of variousother types having a screw adjusting mechanism associated therewith.

The control switch illustrated in the drawing includes an elongatedinsulating base I which carries a switch mechanism including a pair ofstationary contacts 2-2, and a cooperating bridging contact 3.Stationary contacts 22 are mounted side by side within openings adjacentthe lower end of insulating base i and bridging contact I is mountedupon a pivoted insulating contact carrier 4 having a spring 5 associatedtherewith for biasing the same in a direction to hold said bridgingcontact in engagement with said stationary contacts. Contact carrier 4is controlled by a fluid condition responsive device 6 through themedium of a snap operating mechanism including pivoted levers 1 and 8and an over-center spring 9, and said fluid condition arranged adjacentthe underside of said bracket and at a point midway between the endsthereof, and the latter pivot pin being arranged adjacent the upper sideof said bracket at a point adjacent the rear end thereof. Contactcarrier 4 and lever 8 are both pivotally mounted upon pivot pin it andlever I is pivotally mounted upon pivot pin i5. Contact carrier I isprovided with spaced side arms l6 and said side arms are provided withstop rojections I! which are engageable with the underside of bracket I!to limit circuit openingmovement of said contact carrier beyond theposition shown in Fig. 2.

Lever I is provided with spaced side arms for example which straddlecontact carrier 4 and said lever is movable with respect to said contactcarrier between the stop projections l? on the latter, and an adjustablescrew stop i8 which is threaded into an opening in insulating base i.Lever l extends between the side arms of contact carrier 3 and the freeend thereof projects forwardly through a recess in the front wall ofbracket i2. Lever 8 has a pointed rivet i9 fixed to the lower endthereof which engages an indented cup washer 20, and lever i hasapointed rivetiii fixed thereto at a point below pivot pin H whichengages an indented cup washer 22. Spring of the snap operatingmechanism is held under compression between the cup washers 2-0 and 22.

With lever l in the position shown in 2 spring 3 is positioned so thatthe force thereof acts on a line located to the rear of pivot pin M.Lever-'8 is thus biased to move forwardly into engagement with stopprojections I! on contact carrier 4 to hold said contact carrier in openposition, as shown in Fig. 2;. During forward movement of lever I fromthe position shown in Fig. 2 into the position shown in Fig. 1 spring 9assumes a position wherein the force thereof acts on a line located infront of pivot pin I4. Lever 8 then snaps out of the position shown inFig. 2 into engagement with stop I8, and contact carrier I is thusquickly moved into circuit closing position under the action of spring5. During return movement of lever i from the position shown in Fig. iinto the position shown in Fig. 2 spring 3 returns to a position whereinthe force thereof acts on a line located to the rear of pivot pin I4.Lever 8 is then snapped into the position shown in Fig. 2, and duringfinal movement thereof into such position the same engages stopprojections I! on contact; carrier 4 to quickly move the latter intocircuit opening position against the action of spring 5.

Lever 1 is controlled by the fluid condition responsive device 8 and inthe embodiment. illustrated said device comprises a bellows 23 enclosedwithin a cup shaped member 24. Bellows 23 is secured to the rear wall ofcup member 24 and said cup member is fixed tothe rear face of insulatingbase I by rivets 24 which also serve to secure the bracket I2 to thefront face of said insulating base. The front end of bellows 23 has apin 25 fixed thereto which extends through an opening in base I and isprovided with a pointed end which engages a thrust member 26 fixedwithin an opening in lever 1. The front end of thrust member 26 engagesa washer 21.and loading spring III is held under compression betweensaid washer and a nut 23 mounted upon screw II. Nut 23 is held againstrotation by en- Basement with bracket I2 and screw II is rotatablymounted within an opening in the front wall of said bracket and isprovided with a shoulder for engaging the rear side of said wall. Thusupon rotation of screw I I nut 28 is moved axially thereon to vary thedegree of compression of spring I I.

The above described control device may be used in connection withelectric refrigerators to effect starting and stopping of therefrigerator upon given temperatures in the food com-partment thereof.For such service bellows 23 has a closed pipe extension 29 sealed to therear end thereof to be arranged within the cooling compartment of therefrigerator. Pipe extension 29 and bellows 23 contain an expansiblefluid, as methyl chloride, and upon tempera ture changes within thecooling compartment the a avogzso pressure of such fluid varies toeffect operation of bellows 23.

Upon an increase in temperature within the cooling compartment bellows23 expands and at a predetermined temperature determined by the opposingforce of spring ill, lever l is operated to move contact carrier a intocircuit closing position for starting of the refrigerator. Upon a givendecrease in temperature within the cooling compartment bellows 23contracts under the action of spring i0 and lever l is operated to movecontact carrier i into circuit opening position for slppping of therefrigerator. As is apparent, screw ii is adjustable to vary the degreeof compression of spring id for variation of the temperature values atwhich the refrigerator is started and stopped. [is hereinafter setforth, screw ii is adjustable within a given range known as the coldcontrol" range to effect operation of the refrigerator at selectedrefrigerating temperatures, and said screw is also movable to a pointbeyond said range to effect operation of the refrigerator at anabnormally high temperature for defrosting.

In accordance with the present invention screw I I is adjustable by aknob 30 through the medium of a pair of elliptical spur gears 3i and 32.Gears 3! and 32 are of the same shape and size and each is mounted torevolve about one of its foci as a fixed center. Gear 3i is fixed to thefront end of screw H and gear 32 is rotatably mounted upon the frontwall of a cover member 33 which is removably secured to the from; faceof insulating base I. Cover 33 is formed of molded insulating materialand the front. wall thereof is provided with an opening for receivinggear 3 I.

Gear 3! is secured to the front end of screw Ii by a screw 34 and isheld against turning with respect to said screw by a lock washer 35. Asshown in dotted lines in Fig. 3, the rear face of gear 3! has a camprojection 36 formed. thereon which cooperates with a projection 31 onthe front wall of bracket I2 to limit movement of said gear in oppositedirections between extreme positions designated by reference characters011" and 9 in Fig. 4. Cam projection 35 also cooperates with the frontend of lever I and acts upon counterclockwise rotation of gear 3| intooif" position to move said lever into circuit opening position.

Gear 32 has a spindle 38 formed on the rear side thereof which isrotatably supported within an opening in the front wall 01 cover 33.Gear 32 is held in assembled position upon the front wall of cover 33 bya washer 33 secured to the rear end of spindle 38 and knob 30 is fixedto a projection 40 on the front face of gear 32. The

front face of knob 30 is provided with an arrow ll which cooperates witha. stationary dial plate shown in section in Fig. 1 to indicate thetemperature setting of the switch.

Fig. 5 illustrates the various settings of knob 30 and its associatedgear 32, and Fig. 4 illustrates corresponding settings of gear 3| andits associated screw II. With knob 33 in position 9 (Fig. 5) the gears3| and 32 are positioned as shown in Fig. 3, cam projection 33 being inengagement with stop 3'! to prevent countersition shown in Fig. 5. Withgear 31 and screw 9 (Fig. 4) the spring III is compressed to a degree tocause operation of the refrigerator at a low temperature such as isrequired for quick freezing.

Upon clockwise rotation of knob 30, gear 3; acts to drive gear'3| andscrew H in a counterclockwise direction to increase the degree ofcompression of spring l and'thereby increase the temperature values atwhich the refrigerator is started and stopped. As is apparent tfrom Fig.3, during clockwise rotation of knob 30 from position 9 to position 1the pitch radius of gear 32at the point of contact with gear 3|increases, while the pitch radius of gear 3| at the point of contactwith gear 32' decreases. Thus the degree of .angular movement of gear 3|and its associated screw I I per. degree of knob rotation increasesduring movement of said knob from position 9 to position .1. Intheembodiment illustrated the cold control range of screw extendsthrough an angle of 92 and as shown in Fig. 5 said screw is movedthrough said range by movement of the knob 30 and gear 32 through anangle of 118.

In practice it has been found that the operating characteristics of agas filled bellows is such that a given degree of rotation of screw IIat the cold end of its cold control range effects -a greater degree ofvariation in the temperature setting of the switch than is obtained by acorresponding degree of rotation of the adjusting screw at the warm endof said range. Gears 3| and 32 are designed to suit the operatingcharacteristic of the bellows, the same being so proportioned andarranged as to effect adjustment of screw H for corresponding variationsin the temperature setting of the switch upon substantially like degreesof adjustment of knob 30 at opposite ends of its cold control range.

Upon movement of knob 39 beyond its cold control range into the defrostposition (Fig. 5) gear 3| and its associated screw ii are moved intodefrost position (Fig. 4) to increase the loading effect of spring H) toa degree which provides for cycling of the refrigerator at a relativelyhigh defrosting temperature. In the embodiment illustrated knob 30 movesthrough an angle of 142 from position 1 to its defrost position, whereasgear 3| and screw I l are moved through an angle of 178 from position"1. to the defrost position. Also in the embodiment illustrated movementof knob 30 through an angle of 52 from defrost position to off positionef fects a corresponding degree of movement of gear 3| and screw ll.Upon movement of gear 3| and I to move said lever into circuit openingposition for stopping of the refrigerator.

In connection with the foregoing it should be noted that knob 30 ismovable through a rela-. tively wide range for selection of coldcontroltemperatures, and is also adapted upon movement through a relativelysmall range to effect a wide change in the loading effect of spring I0for defrosting. 7 J

In the embodiment illustrated spring I0 is of special design to providea relatively high defrosting temperature upon movement of screw II andits associated gear'3l from position 1 to defrost position. As shown inFig. 1, the end turns of spring II are of lesser pitch than theintermediate turns thereof. The arrangement is such that upon movementof gear 3| and screw II from position 1 into defrost" position the endturns of spring II are brought into engagement to effect a relativelywide increase in the loading effect of said spring.

What we claim as new and desire to secure by Letters Patent is:

1-. The combination with a temperature responsive refrigerator controlswitch including a loading spring and a screw for adjustingsaid springto vary the temperature setting of said said screw through its coldcontrol range, and

less than unity formovement of said screw beyond said cold control rangeinto defrosting position.

2. The combination with a temperature responsive refrigerator controlswitch including a loading spring and a screw for adjusting said springto vary the temperature setting of said switch, said screw being movablewithin a given cold control range for selection of refrigeratingtemperatures and being movable to a point beyond said range to provide arelatively high defrosting temperature, a rotatable manual adjustingknob for said screw and an elliptical gear drive between said knob andsaid screw, said gear drive acting upon movement of said knob in onedirection out of a given extreme position to effect adjustment of saidscrew at an increasing rate from the cold end to the warm end of saidcold control range.

3. The combination with ,a temperature responsive'refrigerator controlswitch including a loading spring and a screw for adjusting said screw Hfrom the defrost position into off a position cam 36 engages the frontend of lever spring to vary the temperature setting of said switch, saidscrew being movable within a given col-d control range for selection ofrefrigerating temperatures and being movable to a point beyond saidrange to provide a relatively high defrosting temperature, a rotatableadjusting knob for said sore and a gear drive between said knob and saiscrew, said gear drive being of varying pitch radius to render the ratioof movement of said knob with respect to said screw greater than unityfor movement of said screw through its cold control range, and less thanunity for movement of said screw beyond said cold controlrange intodefrosting position and said spring being of varying pitch to provide arelatively large increase in the loading efl'ect thereof upon movementof said screw beyond its cold control range into defrosting position.

4. The combination with a temperature responsive refrigerator controlswitch including a loading spring and a screw rotatable to adjust saidspring for variation of the temperature setting of said switch, of a.rotatable manual adjusting member, a drive between said manual-adjustingmember and said screw including adriving gear fixed to said manualadjusting member and a driven gear mounted upon said screw, said gearsbeing of elliptical form to provide varying degrees of adjustment ofsaid screw upon like angular movements of said rotatable adjustingmember in different parts of its range and said screw being releasablyconnected to said driven gear to permit-adjustment of theangularposition of said. screw with respect to said drive.

CLARENCE W. KUHN. ROBERT 0. PERRINE.

